Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Condensed consolidating guarantor financial information (Details) - Senior Notes - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Nov. 20, 2017
4.875% Senior Notes due 2026
Debt Instrument [Line Items]
Debt instrument, face amount	$ 400
Interest rate	4.875%	4.875%
4.625% Senior Notes due 2027
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500
Interest rate	4.625%	4.625%	4.625%